There is a mythical belief by people that if you get malaria, you will die, or you will wake up in malaria dreams for the rest of your life. This is not true.
List of Medicines use for Malaria or Paludisme
1.1 Quinine and related agents1.2 Chloroquine1.3 Amodiaquine1.4 Pyrimethamine1.5 Proguanil1.6 Sulfonamides1.7 Mefloquine1.8 Atovaquone1.9 Primaquine1.10 Artemisinin and derivatives1.11 Halofantrine1.12 Doxycycline1.13 Clindamycin
Quinine and related agents
Quinine has a long history stretching from Peru, and the discovery of the cinchona tree, and the potential uses of its bark, to the current day and a collection of derivatives that are still frequently used in the prevention and treatment of malaria. Quinine is an alkaloid that acts as a blood schizonticidal and weak gametocide against Plasmodium vivax and Plasmodium malariae. As an alkaloid, it is accumulated in the food vacuoles of Plasmodium species, especially Plasmodium falciparum. It acts by inhibiting the hemozoin biocrystallization, thus facilitating an aggregation of cytotoxic heme. Quinine is less effective and more toxic as a blood schizonticidal agent than chloroquine; however, it is still very effective and widely used in the treatment of acute cases of severe P. falciparum. It is especially useful in areas where there is known to be a high level of resistance to chloroquine, mefloquine, and sulfa drug combinations with pyrimethamine. Quinine is also used in post-exposure treatment of individuals returning from an area where malaria is endemic.The treatment regimen of quinine is complex and is determined largely by the parasite's level of resistance and the reason for drug therapy (i.e. acute treatment or prophylaxis). The World Health Organization recommendation for quinine is 20 mg/kg first times and 10 mg/kg 8 hr for 5days where parasites are sensitive to quinine, combined with doxycycline, tetracycline or clindamycin. Doses can be given by oral, intravenous or intramuscular routes. The recommended method depends on the urgency of treatment and the available resources (i.e. sterilised needles for IV or IM injections).
Use of quinine is characterised by a frequently experienced syndrome called cinchonism. Tinnitus (a hearing impairment), rashes, vertigo, nausea, vomiting and abdominal pain are the most common symptoms. Neurological effects are experienced in some cases due to the drug's neurotoxic properties. These actions are mediated through the interactions of Quinine causing a decrease in the excitability of the motor neuron end plates. This often results in functional impairment of the eighth cranial nerve, resulting in confusion, delirium and coma. Quinine can cause hypoglycaemia through its action of stimulating insulin secretion; this occurs in therapeutic doses and therefore it is advised that glucose levels are monitored in all patients every 4–6 hours. This effect can be exaggerated in pregnancy and therefore additional care in administering and monitoring the dosage is essential. Repeated or over-dosage can result in renal failure and death through depression of the respiratory system.
Quinimax and quinidine are the two most commonly used alkaloids related to quinine in the treatment or prevention of malaria. Quinimax is a combination of four alkaloids (quinine, quinidine, cinchoine and cinchonidine). This combination has been shown in several studies to be more effective than quinine, supposedly due to a synergistic action between the four cinchona derivatives. Quinidine is a direct derivative of quinine. It is a distereoisomer, thus having similar anti-malarial properties to the parent compound. Quinidine is recommended only for the treatment of severe cases of malaria.
Warburg's Tincture was a febrifuge developed by Dr Carl Warburg in 1834, which included quinine as a key ingredient. In the 19th-century it was a well-known anti-malarial drug. Although originally sold as a secret medicine, Warburg's Tincture was highly regarded by many eminent medical professionals who considered it as being superior to quinine (e.g. Surgeon-General W. C. Maclean, Professor of Military Medicine at British Army Medical School, Netley). Warburg's Tincture appeared in Martindale: The complete drug reference from 1883 until about 1920. The formula was published in The Lancet 1875.
Chloroquine was, until recently, the most widely used anti-malarial. It was the original prototype from which most methods of treatment are derived. It is also the least expensive, best tested and safest of all available drugs. The emergence of drug-resistant parasitic strains is rapidly decreasing its effectiveness; however, it is still the first-line drug of choice in most sub-Saharan African countries. It is now suggested that it is used in combination with other antimalarial drugs to extend its effective usage. Popular drugs based on chloroquine phosphate (also called nivaquine) are Chloroquine FNA, Resochin and Dawaquin.
Chloroquine is a 4-aminoquinolone compound with a complicated and still unclear mechanism of action. It is believed to reach high concentrations in the vacuoles of the parasite, which, due to its alkaline nature, raises the internal pH. It controls the conversion of toxic heme to hemozoin by inhibiting the biocrystallization of hemozoin, thus poisoning the parasite through excess levels of toxicity. Other potential mechanisms through which it may act include interfering with the biosynthesis of parasitic nucleic acids and the formation of a chloroquine-haem or chloroquine-DNA complex. The most significant level of activity found is against all forms of the schizonts (with the obvious exception of chloroquine-resistant P. falciparum and P. vivax strains) and the gametocytes of P. vivax, P. malariae, P. ovale as well as the immature gametocytes of P. falciparum. Chloroquine also has a significant anti-pyretic and anti-inflammatory effect when used to treat P. vivax infections, and thus it may still remain useful even when resistance is more widespread. According to a report on the Science and Development Network website's sub-Saharan Africa section, there is very little drug resistance among children infected with malaria on the island of Madagascar, but what drug resistance there is exists against chloroquinine.
Children and adults should receive 25 mg of chloroquine per kg given over 3 days. A pharmacokinetically superior regime, recommended by the WHO, involves giving an initial dose of 10 mg/kg followed 6–8 hours later by 5 mg/kg, then 5 mg/kg on the following 2 days. For chemoprophylaxis: 5 mg/kg/week (single dose) or 10 mg/kg/week divided into 6 daily doses is advised. Chloroquine is only recommended as a prophylactic drug in regions only affected by P. vivax and sensitive P. falciparum strains. Chloroquine has been used in the treatment of malaria for many years and no abortifacient or teratogenic effects have been reported during this time; therefore, it is considered very safe to use during pregnancy. However, itching can occur at intolerable level and Chloroquinine can be a provocation factor of psoriasis.
Amodiaquine is a 4-aminoquinolone anti-malarial drug similar in structure and mechanism of action to chloroquine. Amodiaquine has tended to be administered in areas of chloroquine resistance while some patients prefer its tendency to cause less itching than chloroquine. Amodiaquine is now available in a combined formulation with artesunate (ASAQ) and is among the artemisinin-combination therapies recommended by the World Health Organisation. Combination with sulfadoxine=pyrimethamine is no longer recommended (WHO guidelines 2010).The drug should be given in doses between 25 mg/kg and 35 mg/kg over 3 days in a similar method to that used in chloroquine administration. Adverse reactions are generally similar in severity and type to that seen in chloroquine treatment. In addition, bradycardia, itching, nausea, vomiting and some abdominal pain have been recorded. Some blood and hepatic disorders have also been seen in a small number of patients.
Pyrimethamine is used in the treatment of uncomplicated malaria. It is particularly useful in cases of chloroquine-resistant P. falciparum strains when combined with sulfadoxine. It acts by inhibiting dihydrofolate reductase in the parasite thus preventing the biosynthesis of purines and pyrimidines, thereby halting the processes of DNA replication, cell division and reproduction. It acts primarily on the schizonts during the erythrocytic phase, and nowadays is only used in concert with a sulfonamide.
Proguanil (chloroguanide) is a biguanide; a synthetic derivative of pyrimidine. It was developed in 1945 by a British Antimalarial research group. It has many mechanisms of action but primarily is mediated through conversion to the active metabolite cycloguanil. This inhibits the malarial dihydrofolate reductase enzyme. Its most prominent effect is on the primary tissue stages of P. falciparum, P. vivax and P. ovale. It has no known effect against hypnozoites therefore is not used in the prevention of relapse. It has a weak blood schizonticidal activity and is not recommended for therapy of acute infection. However it is useful in prophylaxis when combined with atovaquone or chloroquine (in areas where there is no chloroquine resistance). 3 mg/kg is the advised dosage per day, (hence approximate adult dosage is 200 mg). The pharmacokinetic profile of the drugs indicates that a half dose, twice daily maintains the plasma levels with a greater level of consistency, thus giving a greater level of protection. The proguanil- chloroquine combination does not provide effective protection against resistant strains of P. falciparum. There are very few side effects to proguanil, with slight hair loss and mouth ulcers being occasionally reported following prophylactic use. Proguanil hydrochloride is marketed as Paludrine by AstraZeneca.
Sulfadoxine and sulfamethoxypyridazine are specific inhibitors of the enzyme dihydropteroate synthetase in the tetrahydrofolate synthesis pathway of malaria parasites. They are structural analogs of p-aminobenzoic acid (PABA) and compete with PABA to block its conversion to dihydrofolic acid. Sulfonamides act on the schizont stages of the erythrocytic (asexual) cycle. When administered alone sulfonamides are not efficacious in treating malaria but co-administration with the antifolate pyrimethamine, most commonly as fixed-dose sulfadoxine-pyrimethamine (Fansidar), produces synergistic effects sufficient to cure sensitive strains of malaria.
Sulfonamides are not recommended for chemoprophylaxis because of rare but severe skin reactions experienced. However it is used frequently for clinical episodes of the disease.
Mefloquine was developed during the Vietnam War and is chemically related to quinine. It was developed to protect American troops against multi-drug resistant P. falciparum. It is a very potent blood schizonticide with a long half-life. It is thought to act by forming toxic heme complexes that damage parasitic food vacuoles. It is now used solely for the prevention of resistant strains of P. falciparum despite being effective against P. vivax, P. ovale and P. marlariae. Mefloquine is effective in prophylaxis and for acute therapy. It is now strictly used for resistant strains (and is usually combined with Artesunate). Chloroquine/proguanil or sulfa drug-pyrimethamine combinations should be used in all other Plasmodia infections.The major commercial manufacturer of mefloquine-based malaria treatment is Roche Pharmaceuticals, which markets the drug under the trade name "Lariam". Lariam is fairly expensive at around 3 € per tablet (pricing of the year 2000).
A dose of 15–25 mg/kg is recommended, depending on the prevalence of mefloquine resistance. The increased dosage is associated with a much greater level of intolerance, most noticeably in young children; with the drug inducing vomiting and oesophagitis. It was not recommended for use during the first trimester, although considered safe during the second and third trimesters; nevertheless, in October 2011, the Centers for Disease Control and Prevention (CDC) changed its recommendation and approved use of Mefloquine for both prophylaxis and treatment of malaria in all trimesters, after the Food and Drug Administration (FDA) changed its categorization from C to B. Mefloquine frequently produces side effects, including nausea, vomiting, diarrhea, abdominal pain and dizziness. Several associations with neurological events have been made, namely affective and anxiety disorders, hallucinations, sleep disturbances, psychosis, toxic encephalopathy, convulsions and delirium. Cardiovascular effects have been recorded with bradycardia and sinus arrhythmia being consistently recorded in 68% of patients treated with mefloquine (in one hospital-based study).Mefloquine can only be taken for a period up to 6 months due to side effects. After this, other drugs (such as those based on paludrine/nivaquine) again need to be taken.
Atovaquone is only available in combination with proguanil under the name Malarone, albeit at a price higher than Lariam. It is commonly used in prophylaxis by travellers and used to treat falciparum malaria in developed countries.
Primaquine is a highly active 8-aminoquinolone that is used in treating all types of malaria infection. It is most effective against gametocytes but also acts on hypnozoites, blood schizonticytes and the dormant plasmodia in P. vivax and P. ovale. It is the only known drug to cure both relapsing malaria infections and acute cases. The mechanism of action is not fully understood but it is thought to block oxidative metabolism in Plasmodia.
For the prevention of relapse in P. vivax and P. ovale 0.15 mg/kg should be given for 14 days. As a gametocytocidal drug in P. falciparum infections a single dose of 0.75 mg/kg repeated 7 days later is sufficient. This treatment method is only used in conjunction with another effective blood schizonticidal drug. There are few significant side effects although it has been shown that primaquine may cause anorexia, nausea, vomiting, cramps, chest weakness, anaemia, some suppression of myeloid activity and abdominal pains. In cases of over-dosage granulocytopenia may occur.
Artemisinin and derivatives
Artemisinin is a Chinese herb (qinghaosu) that has been used in the treatment of fevers for over 1,000 years, thus predating the use of Quinine in the western world. It is derived from the plant Artemisia annua, with the first documentation as a successful therapeutic agent in the treatment of malaria is in 340 AD by Ge Hong in his book Zhou Hou Bei Ji Fang (A Handbook of Prescriptions for Emergencies). Ge Hong extracted the artemesinin using a simple macerate, and this method is still in use today. The active compound was isolated first in 1971 and named artemsinin. It is a sesquiterpene lactone with a chemically rare peroxide bridge linkage. It is this that is thought to be responsible for the majority of its anti-malarial action, although the target within the parasite remains controversial. At present it is strictly controlled under WHO guidelines as it has proven to be effective against all forms of multi-drug resistant P. falciparum, thus every care is taken to ensure compliance and adherence together with other behaviors associated with the development of resistance. It is also only given in combination with other anti-malarials.
Artemisinin has a very rapid action and the vast majority of acute patients treated show significant improvement within 1–3 days of receiving treatment. It has demonstrated the fastest clearance of all anti-malarials currently used and acts primarily on the trophozite phase, thus preventing progression of the disease. Semi-synthetic artemisinin derivatives (e.g. artesunate, artemether) are easier to use than the parent compound and are converted rapidly once in the body to the active compound dihydroartemesinin. On the first day of treatment 20 mg/kg should be given, this dose is then reduced to 10 mg/kg per day for the 6 following days. Few side effects are associated with artemesinin use. However, headaches, nausea, vomiting, abnormal bleeding, dark urine, itching and some drug fever have been reported by a small number of patients. Some cardiac changes were reported during a clinical trial, notably non specific ST changes and a first degree atrioventricular block (these disappeared when the patients recovered from the malarial fever).
Artemether is a methyl ether derivative of dihydroartemesinin. It is similar to artemesinin in mode of action but demonstrates a reduced ability as a hypnozoiticidal compound, instead acting more significantly to decrease gametocyte carriage. Similar restrictions are in place, as with artemesinin, to prevent the development of resistance, therefore it is only used in combination therapy for severe acute cases of drug-resistant P. falciparum. It should be administered in a 7 day course with 4 mg/kg given per day for 3 days, followed by 1.6 mg/kg for 3 days. Side effects of the drug are few but include potential neurotoxicity developing if high doses are given.
Artesunate is a hemisuccinate derivative of the active metabolite dihydroartemisin. Currently it is the most frequently used of all the artemesinin-type drugs. Its only effect is mediated through a reduction in the gametocyte transmission. It is used in combination therapy and is effective in cases of uncomplicated P. falciparum. The dosage recommended by the WHO is a 5 or 7 day course (depending on the predicted adherence level) of 4 mg/kg for 3 days (usually given in combination with mefloquine) followed by 2 mg/kg for the remaining 2 or 4 days. In large studies carried out on over 10,000 patients in Thailand no adverse effects have been shown.
Dihydroartemisinin is the active metabolite to which artemesinin is reduced. It is the most effective artemesinin compound and the least stable. It has a strong blood schizonticidal action and reduces gametocyte transmission. It is used for therapeutic treatment of cases of resistant and uncomplicated P. falciparum. 4 mg/kg doses are recommended on the first day of therapy followed by 2 mg/kg for 6 days. As with artesunate, no side effects to treatment have thus far been recorded.Arteether is an ethyl ether derivative of dihydroartemisinin. It is used in combination therapy for cases of uncomplicated resistant P. falciparum. The recommended dosage is 150 mg/kg per day for 3 days given by IM injections. With the exception of a small number of cases demonstrating neurotoxicity following parenteral administration no side effects have been recorded.
Halofantrine is a relatively new drug developed by the Walter Reed Army Institute of Research in the 1960s. It is a phenanthrene methanol, chemically related to Quinine and acts acting as a blood schizonticide effective against all plasmodium parasites. Its mechanism of action is similar to other anti-malarials. Cytotoxic complexes are formed with ferritoporphyrin XI that cause plasmodial membrane damage. Despite being effective against drug resistant parasites, halofantrine is not commonly used in the treatment (prophylactic or therapeutic) of malaria due to its high cost. It has very variable bioavailability and has been shown to have potentially high levels of cardiotoxicity. It is still a useful drug and can be used in patients that are known to be free of heart disease and are suffering from severe and resistant forms of acute malaria. A popular drug based on halofantrine is Halfan. The level of governmental control and the prescription-only basis on which it can be used contributes to the cost, thus halofantrine is not frequently used.
A dose of 8 mg/kg of halofantrine is advised to be given in three doses at six hour intervals for the duration of the clinical episode. It is not recommended for children under 10 kg despite data supporting the use and demonstrating that it is well tolerated. The most frequently experienced side-effects include nausea, abdominal pain, diarrhea, and itch. Severe ventricular dysrhythmias, occasionally causing death are seen when high doses are administered. This is due to prolongation of the QTc interval. Halofantrine is not recommended for use in pregnancy and lactation, in small children, or in patients that have taken mefloquine previously. Lumefantrine is a relative of halofantrine that is used in some combination antimalarial regimens.
Probably one of the more prevalent antimalarial drugs prescribed, due to its relative effectiveness and cheapness, doxycycline is a tetracycline compound derived from oxytetracycline. The tetracyclines were one of the earliest groups of antibiotics to be developed and are still used widely in many types of infection. It is a bacteriostatic agent that acts to inhibit the process of protein synthesis by binding to the 30S ribosomal subunit thus preventing the 50s and 30s units from bonding. Doxycycline is used primarily for chemoprophylaxis in areas where chloroquine resistance exists. It can also be used in combination with quinine to treat resistant cases of P. falciparum but has a very slow action in acute malaria, and should not be used as monotherapy.
When treating acute cases and given in combination with quinine; 100 mg of doxycycline should be given per day for 7 days. In prophylactic therapy, 100 mg (adult dose) of doxycycline should be given every day during exposure to malaria.The most commonly experienced side effects are permanent enamel hypoplasia, transient depression of bone growth, gastrointestinal disturbances and some increased levels of photosensitivity. Due to its effect of bone and tooth growth it is not used in children under 8, pregnant or lactating women and those with a known hepatic dysfunction.
Tetracycline is only used in combination for the treatment of acute cases of P. falciparum infections. This is due to its slow onset. Unlike doxycycline it is not used in chemoprophylaxis. For tetracycline, 250 mg is the recommended adult dosage (it should not be used in children) for 5 or 7 days depending on the level of adherence and compliance expected. Oesophageal ulceration, gastrointestinal upset and interferences with the process of ossification and depression of bone growth are known to occur. The majority of side effects associated with doxycycline are also experienced.
Clindamycin is a derivative of lincomycin, with a slow action against blood schizonticides. It is only used in combination with quinine in the treatment of acute cases of resistant P. falciparum infections and not as a prophylactic. Being more expensive and toxic than the other antibiotic alternatives, it is used only in cases where the Tetracyclines are contraindicated (for example in children).Clindamycin should be given in conjunction with quinine as a 300 mg dose (in adults) four times a day for 5 days. The only side effects recorded in patients taking clindamycin are nausea, vomiting and abdominal pains and cramps. However these can be alleviated by consuming large quantities of water and food when taking the drug. Pseudomembranous colitis (caused by Clostridium difficile) has also developed in some patients; this condition may be fatal in a small number of cases.
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